Ski propelling device

ABSTRACT

A device that is selectively projectable below a ski bottom to propel a ski across snow covered ground. The device includes a pair of pulleys mounted to the ski for heightwise movement between upper and lower positions and an endless belt extending about and between the pulleys. The belt has a bottom run that is located above the ski bottom when the pulleys are in the upper positions and projects through a slot in the ski below the ski bottom when the pulleys are in the lowered positions. An engine, mounted to the skier&#39;&#39;s back, is connected to one of the pulleys by a flexible cable. A propelling mechanism operates in response to the turning on of the engine and the rotation of the flexible cable to cause the pulleys to move downwardly so as to project the bottom run below the bottom of the ski and to rotate the pulleys in such a direction as to move the bottom run rearwardly to thereby propel the ski forwardly.

United States Patent [191 McLeod 11] 3,809,173 1451 May 7,1974

[ SKI PROPELLING DEVICE {76] Inventor: Duncan T. McLeod, 610 W. SecondAve., Anchorage, Alaska 99501 [22] Filed: Aug. 21, 1972 21 Appl. No.:282,064

[52] US. Cl 180/5 R, ISO/9.5, 280/11.1 ET [51] Int. Cl 862m 27/02 [58]Field of Search 180/5 R, 1 G, 9.5, 9.52;

280/ll.1 ET, 11.13 C, 11.13 Z

[56] References Cited UNITED STATES PATENTS 2,339,886 1/1944 Shannon180/5 R Primary Examiner-Richard J. Johnson Assistant Examiner-ReinhardJ. Eisenzopf Attorney, Agent, or FirmD. Paul Weaver 5 7 ABSTRACT Adevice that is selectively projectable below a ski bottom to propel aski across snow covered ground. The device includes a pair of pulleysmounted to the ski for heightwise movement between upper and lowerpositions and an endless belt extending about and between the pulleys.The belt has a bottom run that is located above the ski bottom when thepulleys are in the upper positions and projects through a slot in theski below the ski bottom when the pulleys are in the lowered positions.An engine, mounted to the skiers back, is connected to one of thepulleys by a flexible cable. A propelling mechanism operates in responseto the turning on of the engine and the rotation of the flexible cableto cause the pulleys to move downwardly so as to project the bottom runbelow the bottom of the ski and to rotate the pulleys in such adirection as to move the bottom run rearwardly to thereby propel the skiforwardly.

10 Claims, 9 Drawing Figures PATENTEDIAY H914 3.809.173

sum 1 or 3 FIG. 1

PATENTED W 7 I974 SHEET 3 OF 3 FIG. 7

FIG. 8

l SKI PROPELLING DEVICE BACKGROUND OF THE INVENTION When a skier ismoving on snow across a level area or an uphill slope, it is desirablefor him to have a powered mechanism in his skis to propel him across theground to save him the exertion of going across the level ground oruphill slope. In order for the skier to be able to go downhill withoutinterference from the powered mechanism, the powered mechanism should beout of interfering relationship with the ski bottom at that time.

U.S. Pat. No. 2,625,229 shows propelling mechanisms so mounted to a skithat the propelling mechanism and the ski must be manually inverted 180in order to move the propelling mechanisms between op erative andinoperative positions.

US. Pat. No. 2,254,320 shows an ice skate that incorporates a propellingmechanism that is mounted to the skate for heightwise movement so thatit can be moved heightwise of the skate runner to thereby regulate theengagement of the propelling mechanism with the ice over which the skateis driven.

SUMMARY OF THE INVENTION This invention is concerned with a propellingdevice for a ski that operates in a more effective and efficient mannerthan has heretofore been devised and that, at the control of the skier,can move from a position wherein it is above the bottom of the ski so asnot to in terfere with a downhill movement of the ski to a positionwherein it is below the bottom of the ski where it is effective to movethe skier across level ground or uphill slopes.

A first aspect of the invention is concerned with a mechanism for movinga bottom run of the propelling device between an upper position abovethe ski bottom and a lower position below the ski bottomandforautomatically rendering the bottom run efiective to propel the ski whenit is in its lower position. This is accomplished by providing poweredmeans that is operably connected to the propelling mechanism insuch amanner that the turning on of the powered means causes the bottom run tomove from the upper position to the lower position and to also cause thebottom run to move rearwardly to thereby propel the Ski forwardly. Theconnection between the powered means and the propelling mechanism is soconstructed that the shut ting off of the powered means causes thebottomrun to move from the lower position to the upper position and alsocauses the rearward movement of the bottom run to stop.

A second aspect of the invention is concerned with the construction ofthe propelling mechanismthat enables it to operate in an effectivemanner. This con struction includes a pair of spaced pulleys mounted tothe ski for heightwise movement and an endless belt extending about andbetween the pulleys, the portion of the belt extending between thepulley bottoms providing the bottom run. The pulleys are movable betweenan upper position wherein the bottom run is above the ski bottom and alower position wherein the bottom run is below the ski bottom. The skihas a slot that accommodates the bottom run in its lower position. Adrive mechanism is so connected to the pulleysas to rotate them in adirection to impart rearward movement to i 2 the bottom run when thepulleys are in their lower positions.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is anelevation of an enginethat is mountable on a skiers back, a pair of skis having the propellingdevices mounted thereon, and flexible cables extending between'theengine and the propelling mechanisms;

FIG. 2 is a side elevation of a ski having the propelling mechanismmounted thereon;

FIG. 3 is a bottom view of the ski;

FIG. 4 is a view of a front pulley and a back pulley that form a part ofthe propelling mechanism and is taken on the line 4-4 of FIG. 2;

FIG. 5 is a section taken on the line 5-5 of FIG. 2;

FIG. 6 is a section taken on the line 6-6 of FIG. 2;

FIG. 7 is a section taken on the line 7-7 of FIG. 2;

FIG. 8 is a section taken on the line 8-8 of FIG. 7; and

FIG. 9 is a section taken on the line 9-9 of FIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. I shows an engine 10attached to a frame 12 that is mountable on a skiers back by straps 14that extend over the shoulders and belt elements 16 that extend aboutthe waist. The engine has a one-way drive and when it is turned on can,by means of a gear train 18, rotate in opposite directions two flexiblecables 20 that depend from the frame 12. A strap 22, mountedto eachcable 20, is intended to be buckled around a leg of the skier above theknee. The straps 22 function to stabilize the cables 20 when the cablesextend between the skiers back and a pair of skis 24in the manner setforth below.

Referring to FIGS. 2-6, each ski24 has a pair of laterally spaced frontbrackets 26 rigidly mounted thereto. Rearwardly of the front brackets, apair of spaced rear brackets 28 are pivotedon pins 30 that are rigidlymounted to each skiby means of angles 32. The rear brackets 28extendrearwardly of the pins 30 and are yieldably urged downwardly about theaxis of the pins 30 so as to bear against the tops of the skis bysprings 34 that are entwined aboutthe pins 30and extend between theangles 32 and the brackets 28. A front axle 36 extends throughaligneddownwardly and forwardly inclinedtracks in the form of slots 38formed in the front brackets 26. A rear axle 40extends through alignedtracks in the form of slots 42 formed in the rear brackets 28.Clevisarms 44 ofa clevis 46 are mounted to the axle 36 and a frontpulley 48 is rotatably mounted to the axle 36 between the clevis arms44. Clevis arms 50of a clevis'52 aremounted to the axle 40, and a backpulley 54 is mountedto the axle 40 in the manner described below. Anextension 56 of the clevis 46 is slidably and nonrotatably received in asocket 58 of the clevis 52. A spring 60 interposed between the extension56 and the base of the socket 58 and 52. The guides 62 and 64 extendbetween the pulleys 48 and 54. An endless cleated belt 66 extends aboutthe pulleys 48 and 54 and is guided therebetween by the belt guides 62and 64. The spring 60, by yieldably urging the pulleys 48 and 54 awayfrom each other, enables the belt 66 to extend tautly about the pulleys48 and 54. The bottom run of the belt 66 extends through a slot 68 thatextends through the ski 24.

Referring to FIG. 7, the axle 40 is formed of aligned sections 70 and72. The pulley 54 is rigidly mounted on a pulley hub 74 formed of asleeve 76 that extends between and is secured to pulley hub face plates78. One of the face plates 78 is rotatably mounted on the axle section70 and the other face plate 78 is rotatably mounted on the axle section72. A sleeve 80 is located within the hub 74 and is spaced inwardly ofthe inner periphery of the sleeve 76 by bushings 82. The axle section 70extends through the left (FIG. 7) face plate 78 and is threadedlysecured to the sleeve 80 so that the sleeve 80 is, in effect, a part ofthe axle section 70. The axle section 72 extends through the right faceplate 78 and into the axial aperture 84 in the sleeve 80. A spring 86 islocated in the aperture 84 and is interposed between the inner ends ofthe axle sections 70 and 72. A pin 88, projecting outwardly of the axlesection 72 within the sleeve 80, is received in an inclined slot 90 onthe inner periphery of the sleeve 80. Fibrous clutch washers 92 arerotatably mounted to the axle sections 70 and 72 outwardly of the faceplates 78 and gears 94 are rotatably mounted to the axle sections 70 and72 outwardly of the washers 92. A clamping member in the form of a snapring 96 is mounted in an annular groove in the axle section 70,outwardly of its associated gear 94, so as to be incapable of axialmovement with respect to the axle section 70. Another clamping member inthe form of a nut 98 is threaded onto the axle section 72 outwardly ofits associated gear 94.

Outwardly of the snap ring 96, the axle section 70 is rotatably mountedin a bushing 100. The flexible cable includes a sheath 102, that isattached to prongs 104 on the bushing 100, and a rotatable core 106. Thecore 106 terminates in a prong 108 that is nonrotatably received in anaxial opening in the outer end of the axle section 70. Thebushing 100 isoval shaped, and nonrotatably mounted to the bushing 100 between aflange 110 of the bushing and a snap ring 111 fitted to the bushing areone of the rear brackets 28 and one of the clevis arms 50.

Outwardly of the nut 98, the axle section 72 is rotatably mounted in abushing 112. The bushing 112 is also oval shaped (FIG. 8), andnonrotatably mounted to the bushing 112 between a flange 114 of thisbushing and a snap ring 116 fitted to this bushing are the other of therear brackets 28 and the other of the clevis arms 50.

Referring to FIG. 8, the oval shape of the bushings 100 and 112 enablethem to be slidably received in the slots 42 of the rear brackets 28 sothat they can move along the axes of the slots 42 but cannot rotate withrespect to the slot axes. The oval shapes of the bushings 100 and 112enable them to be nonrotatably mounted to the clevis arms 50. Each ofthe slots 42 has a rear upright portion 118 whose bottom arcs downwardlyand forwardly into an arcuate portion 119 and thence forwardly into aprone portion 120. Each gear 94 is in mesh with teeth 121 on a rack 122.The racks 122 are mounted to the brackets 28 by spacers 123 (FIG. 7),

are located outwardly of the slots 42, and are shaped similarly to theslots 42.

A washer 124 is mounted to the bushing 100 between its flange I10 andits associated rear bracket 28, and another washer 124 is mounted to thebushing 112 between its flange 114 and its associated rear bracket 28. Aspring 126 extends between the top of each washer 124 and a fastener 128(FIG. 2) that is secured to the top of each rear bracket 28.

Referring to FIGS. 7 and 9, an anchor spring 130 is mounted to the outerend of the axle section 72 outwardly of the bushing 112. The spring 130extends upwardly of the axle section 72 and is adapted to bear against apin 132 that is mounted to and extends outwardly of the associated rearbracket 28 above the axle section 72.

When the engine 10 is turned off, the flexible cables 20 are notrotating. The spring 126 at this time are urging the bushings 100 and112 upwardly in the slots 42 to a position wherein the spring 130 bearsagainst the pin 132 and the rear axle 40 together with the gears 44 andthe back pulley 54 are in an upper position with respect to the rearbrackets 28. The bushings 100 and 112 are, at this time, either in theportions 118 or the portions 119 of the slots 42, and the gears 94 arein mesh with the racks 122. The front axle 36 is, at this time, locatedat the rear end of the slots 38. Due to the elevated position of thefront and rear axles, the bottom run of the belt 66 is located upwardlyof the bottoms of the skis 24 and therefore will not interfere with thenormal skiing operation of the skier.

At this time, the snap ring 96 and the nut 98 are relatively far apartdue to the position of the pin 88 in the slot 90 causing the inner endsof the axle portions and 72 to be relatively remote from each other. Thegears 94 are therefore, at this time, not being pressed inwardly againstthe clutch washers 92 and the hub face plates 78.

When the skier is at a level area or at an uphill slope wherein hewishes to use the belts 66 to propel him, he turns on the engine 10 torotate the flexible cables 20 to thus cause each axle section 70 andsleeve to rotate in a direction to cause the pins 88 and the slots tocooperate to move the axle sections 72 towards the axle sections 70against the forces of the springs 86 to thereby force each nut 98towards its associated snap ring 96 to thus clamp the gears 94, theclutch washers 92 and the pulley hub 74 between the now rotating snapring 96 and nut 98. This clamping action causes the gears 94 and thepulley hub 74 to also rotate.

The gears 94, for each ski, are rotated in such a direction as to causethem to move downwardly of the racks 122 with the bushings and 112moving downwardly and forwardly in the slots 42 into the slot portions120. The downward and forward movement of the bushings 100 and 112causes a corresponding downward and forward movement of each pulley hub74 and each back pulley 54 against the forces of the springs 126 withthe anchor springs moving downwardly of the pins 132.

Each back pulley 54 is rotated in such a direction as to move the bottomrun of the belt 66 rearwardly and the top run of the belt 66 forwardly,this movement of the belt causing the front pulley 48 to rotate aboutthe axis of the axle 36. The downward movement of each back pulley 54causes the rear portion of the bottom run of the belt 66 to descendbelow the bottom of the ski 24. The forward movement of each back pulley54 in the slot portion 120 causes the spring 60 to push the front pulley48 downwardly and forwardly in the slots 38 so that the front portion ofthe bottom run of the belt 66 is also caused to descend below the bottomof the ski 24.

The rearward movements of the bottom runs of the belts 66 causes thecleats in the belt to grip the snow so as to impel the skis, togetherwith the skier, forwardly. This forward impetus given to the skis andthe skier causes the bushings 100, 112 to move forwardly into the frontsof the slot portions 120 to thus move the gears 94 forwardly of the rackteeth 121 where the gears are no longer in mesh with the rack teeth tothus enable the gears to rotate in place as long as power is applied tothe gears from the flexible cables 20.

When the lower runs of the belts 66 are projected below the bottoms ofthe skis 24 to propel the skis and the skier forwardly, they areupwardly and forwardly inclined as indicated in phantom in FIG. 2. Thisenables the teeth on the belts to dig progressively deeper into the snowas the bottom runs of the belts move rearwardly to enhance propellingefficiency of the belts. The propelling efficiency of the belts is alsoenhanced by virtue of the fact that the belts are located on the rearends of the skis so that the snow engaged by the belts has beencompressed by the forward ends of the skis.

When the skier reaches a downhill slope, he shuts off the engine toterminate the rotation of the flexible cables and thus shuts off thepower to the axles42 which will continue to rotate for a period due toinertia. The bottom run of the belt 60, at this time, while still movingrearwardly to some extent due to inertia, will drag in the snow andtherefore cause the hubs 100, 112 to move rearwardly in the slotportions 120 and the axles to move rearwardly in the slot portions 120and the axles 36 to move rearwardly in the slots 38. The rack teeth 121cooperative with the gear 94 mounted to the axle section 70 projectfurther forwardly than the rack teeth 121 cooperative with the gear94mounted to the axle section 72. The engagement of the former gear withits associated rack teeth during the rearward movement of the formergear will substantially decrease the rotational speed of the former gearto substantially decrease the rotational speedof the axle section 70 soas to produce relative rotationbetween the axle sections 70 and 72. Thisrelative rotation enables the cooperation between the pin 88and the slot90 and the force of the spring 86 to cause the axle section 72 to moveaway from the axle section 70to thus release the pulley hub 74 and thepulley 54 from the clamping effect of the snap ring% and the nut 98, thepulley hub 74 now rotating by inertia about the bushings 82 until itcoasts to a stop. Shortly after the engagement of the former gear withits associated rack teeth, the latter gear meshes with its associatedrack teeth and the gears 94 together with the bushings 100, 112, theaxle 40, the pulley hub 74, and the back pulley 54are moved rearwardlyand upwardly of the slots 42 by the springs 126.

until the anchor spring 130 engages the pin 132. The rearward and upwardmovement of the back pulley 54 causes the belt 66 to apply pressure tothe front pulley 48 to move the front pulley upwardly and rearwardly ofthe slots 38 so that the bottom run of the belt 66 is raised upwardly ofthe ski 24 and the skier can use the skisin the ordinary manner inskiing downhill.

As stated above, the rear brackets 28 are yieldably urged downwardlyabout the axis of the pins 30 by the springs 32. If the skis 24 are onrelatively hard snow, the resistance of the snow may inhibit thedownward projection of the bottom run of the belt-66 when the flexiblecables 20 are caused to rotate by the engine 10. The yieldable mountingof the brackets 28 to the skis 24 enables the brackets 28 to moveupwardly of the skis about the axis of the pins 30, should snowresistance be encountered, while still enabling the bottom runs of thebelts 66 to be projected downwardly of the bottoms of the skis 24.

I claim:

1. A ski propelling device comprising: a ski; a propelling mechanism,having a rearwardly movable bottom run, mounted to the ski forheightwise movement between an upper position wherein the bottom run isabove the ski bottom and a lower position wherein the bottom run isbelow the ski bottom; powered means operably connected to the propellingmechanism effective, when turned on, to move the bottom run rear-'wardly; means for retaining the propelling mechanism in said upperposition when the powered means is shut off; means responsive to theturning on of the powered means to move the propelling mechanism fromsaid upper position to said lower position; and means responsive to theshutting off of the powered means to return the propelling mechanismfrom said lower position to said upper position.

2. The propelling device of claim 1 wherein the ski has a slot extendingtherethrough andwherein said bottom run is mounted for heightwisemovement in the slot.

3. The propelling device of claim 1 wherein the propelling devicecomprises an endless belt having said bottom run incorporated therein.

4. The propelling device of claim 1 wherein said pro pelling devicecomprises: a pulley havingsaid bottom run mounted thereto; meansmounting said pulley to the ski for said heightwise movement; meansurging the pulley to said upper position; means effective toconcomitantly lower the pulley so as to move the bottom run from saidupper position to said lower position and to rotate the pulley in adirection to move the bottom run rearwardly in response to the turningon of said powered means; and means effective to concomitantly raise thepulley so as to return the bottom run from said lower position tosaidupper position and terminate the rotation of the pulley in responseto the shutting off of the powered means.

5. The propelling device of claim 4further comprising: an axle having afirst sectionand a second section, said sections being so constructedand arranged as to be capable of having relative rotation and axialmovement; connecting means so connecting the sections as to yieldablyurge them axially apart and to enable the second section to move closerto the first section in response to rotation of the firstsection. and tothen enable the two sections to rotate in unison; meansconnecting thefirst section to said powered means; a pair of brackets mounted to andextending upwardly of the ski; a track in each bracket having an uprightportion that joins a forwardly projecting prone portion; a bushing,rotatably mounted to each axle section, mounted for movement in eachtrack; means yieldably urging the bushings upwardly of the tracks; ahub, to which the pulley is secured, having a pair of spaced faceplates,

a first of said face plates being rotatably mounted on said first axlesection and a second of said face plates being mounted on said secondaxle section; a clamping member mounted against axial movement to eachaxle section outwardly of each face plate; a gear mounted to each axlesection for rotation and axial movement on the axial section betweeneach clamping member and its associated face plate; rack teeth somounted to each bracket as to be in mesh with the gears when the hubsare in all portions of the track except for the forwardmost ends of thetrack prone portions; and a slot extending through the ski between thebrackets through which the pulley may project.

6. The propelling device of claim wherein said axle sections projectthrough and inwardly of their associated face plates and wherein saidconnecting means connecting the axle sections comprises: a sleeveforming a part of said first axle section, located between the faceplates, having an aperture that receives the innermost end of the secondaxle section; a spring located within the aperture extending between theaxle sections so as to yieldably urge the axle sections apart; a slot inthe sleeve that is inclined with respect to the axle axis; and a pinprojecting outwardly of said second axle section that is received in theslot.

7. The propelling device of claim 5 wherein said powered means comprisesan engine connected to a flexible cable having a rotatable core mountedin a sheath; and wherein said means connecting said first axle sectionto said powered means comprises: a prong in the end of the core remotefrom the engine that is nonrotatably received in said first axlesection; and a mounting of the end of the sheath remote from the engineto the bushing associated with said first axle section.

8. The propelling device of claim 5 further comprising: a second pair ofbrackets mounted to and projecting upwardly of the ski forwardly of thefirst mentioned pair of brackets; a downwardly and forwardly inclinedtrack in each of said second pair of brackets; a second axle rotatablymounted for movement in said second bracket tracks; a second pulleyrotatably mounted to said second axle; spring means interposed betweenthe first mentioned pulley and second pulley yieldably urging the secondpulley forwardly of the first mentioned pulley, whereby downward andforward movement of the first mentioned pulley through said firstmentioned bracket tracks will cause the spring means to move the secondpulley downwardly and forwardly in said second bracket tracks; anendless belt extending about and between the first mentioned pulley andsaid second pulley, said bottom run being incorporated in said endlessbelt; and said slot extending lengthwise of the ski between the firstmentioned pair of brackets and said second pair of brackets, said slotbeing so dimensioned that the bottom run of the endless belt may projecttherethrough.

9. The propelling device of claim 8 wherein said pulleys and said tracksare so constructed and arranged that said bottom run extends rearwardlyand downwardly between said pulleys when said pulleys have been moveddownwardly.

10. The propelling device of claim 5 wherein said brackets are mountedto the ski for heightwise movement; and further comprising: meansyieldably urging the brackets downwardly against the top of the ski.

1. A ski propelling device comprising: a ski; a propelling mechanism,having a rearwardly movable bottom run, mounted to the ski forheightwise movement between an upper position wherein the bottom run isabove the ski bottom and a lower position wherein the bottom run isbelow the ski bottom; powered means operably connected to the propellingmechanism effective, when turned on, to move the bottom run rearwardly;means for retaining the propelling mechanism in said upper position whenthe powered means is shut off; means responsive to the turning on of thepowered means to move the propelling mechanism from said upper positionto said lower position; and means responsive to the shutting off of thepowered means to return the propelling mechanism from said lowerposition to said upper position.
 2. The propelling device of claim 1wherein the ski has a slot extending therethrough and wherein saidbottom run is mounted for heightwise movement in the slot.
 3. Thepropelling device of claim 1 wherein the propelling device comprises anendless belt havinG said bottom run incorporated therein.
 4. Thepropelling device of claim 1 wherein said propelling device comprises: apulley having said bottom run mounted thereto; means mounting saidpulley to the ski for said heightwise movement; means urging the pulleyto said upper position; means effective to concomitantly lower thepulley so as to move the bottom run from said upper position to saidlower position and to rotate the pulley in a direction to move thebottom run rearwardly in response to the turning on of said poweredmeans; and means effective to concomitantly raise the pulley so as toreturn the bottom run from said lower position to said upper positionand terminate the rotation of the pulley in response to the shutting offof the powered means.
 5. The propelling device of claim 4 furthercomprising: an axle having a first section and a second section, saidsections being so constructed and arranged as to be capable of havingrelative rotation and axial movement; connecting means so connecting thesections as to yieldably urge them axially apart and to enable thesecond section to move closer to the first section in response torotation of the first section and to then enable the two sections torotate in unison; means connecting the first section to said poweredmeans; a pair of brackets mounted to and extending upwardly of the ski;a track in each bracket having an upright portion that joins a forwardlyprojecting prone portion; a bushing, rotatably mounted to each axlesection, mounted for movement in each track; means yieldably urging thebushings upwardly of the tracks; a hub, to which the pulley is secured,having a pair of spaced face plates, a first of said face plates beingrotatably mounted on said first axle section and a second of said faceplates being mounted on said second axle section; a clamping membermounted against axial movement to each axle section outwardly of eachface plate; a gear mounted to each axle section for rotation and axialmovement on the axial section between each clamping member and itsassociated face plate; rack teeth so mounted to each bracket as to be inmesh with the gears when the hubs are in all portions of the trackexcept for the forwardmost ends of the track prone portions; and a slotextending through the ski between the brackets through which the pulleymay project.
 6. The propelling device of claim 5 wherein said axlesections project through and inwardly of their associated face platesand wherein said connecting means connecting the axle sectionscomprises: a sleeve forming a part of said first axle section, locatedbetween the face plates, having an aperture that receives the innermostend of the second axle section; a spring located within the apertureextending between the axle sections so as to yieldably urge the axlesections apart; a slot in the sleeve that is inclined with respect tothe axle axis; and a pin projecting outwardly of said second axlesection that is received in the slot.
 7. The propelling device of claim5 wherein said powered means comprises an engine connected to a flexiblecable having a rotatable core mounted in a sheath; and wherein saidmeans connecting said first axle section to said powered meanscomprises: a prong in the end of the core remote from the engine that isnonrotatably received in said first axle section; and a mounting of theend of the sheath remote from the engine to the bushing associated withsaid first axle section.
 8. The propelling device of claim 5 furthercomprising: a second pair of brackets mounted to and projecting upwardlyof the ski forwardly of the first mentioned pair of brackets; adownwardly and forwardly inclined track in each of said second pair ofbrackets; a second axle rotatably mounted for movement in said secondbracket tracks; a second pulley rotatably mounted to said second axle;spring means interposed between the first mentioned pulley and secondpulley yieldably urging the second pulley forwardly of the firstmentioned pulley, wHereby downward and forward movement of the firstmentioned pulley through said first mentioned bracket tracks will causethe spring means to move the second pulley downwardly and forwardly insaid second bracket tracks; an endless belt extending about and betweenthe first mentioned pulley and said second pulley, said bottom run beingincorporated in said endless belt; and said slot extending lengthwise ofthe ski between the first mentioned pair of brackets and said secondpair of brackets, said slot being so dimensioned that the bottom run ofthe endless belt may project therethrough.
 9. The propelling device ofclaim 8 wherein said pulleys and said tracks are so constructed andarranged that said bottom run extends rearwardly and downwardly betweensaid pulleys when said pulleys have been moved downwardly.
 10. Thepropelling device of claim 5 wherein said brackets are mounted to theski for heightwise movement; and further comprising: means yieldablyurging the brackets downwardly against the top of the ski.